A protist is a unicellular eukaryote, single-celled, and microscopic. A protist has multicellular forms and some relatively complex giants. Some examples of protists include the Paramecium and the Euglena. Fungi are constructed of hyphae, septa, and mycelium. They have cell walls that are made of chitin. Fungi include mold, yeasts, and lichens and they can act as both decomposers and pathogens. Although it is a pathogen, fungi can be commercially important to humans, such as people eating mushrooms, blue cheese, and Roquefort. Bacteriophages are viruses that attack the cell. Most bacterial walls contain peptidoglycan, which consists of polymers of modified sugars cross-linked by short polypeptides that vary from species to species. Gram stain can determine whether the bacteria is gram-positive or gram-negative. A gram-positive bacteria is when the cell walls has a big amount of peptidoglycan. A gram-negative bacteria has less peptidoglycan but more lipopolysaccharides, carbonhydrates bonded to lipids. Pathogenic gram-negative bacteria is often more harmful because their lipopolysaccharides may be toxic and this outer membrane also protects them. There are three basic genetic recombination for bacteria: transformation, conjugation, and transduction. Transformation is the uptake of genes from the environment. Conjugation is the direct transfer of genetic material between prokaryotes. Transduction occurs when the virus transfers the gene. Endospores in bacteria allow the bacteria to thrive in harsh conditions, such as boiling temperature or hydrate and revive to the cology-producing state. Viruses are noncellular obligate intracellular parasites that attack cells. Viruses can undergo either lytic cycle or lysogenic cycle. Three main important parts of the virus is its tail, DNA/RNA, and protein coat. A prion is a protein infectious agent that does not reproduce by itself and may be linked to several degenerative brain diseases. A viron are small tiny molecules of naked circular RNA that infect plants.
Source: Campbell Book
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